Switch-rheostat



March 3, 1964 J. R. KLEMM I 3,123,792

' swTcH-RHEOSTAT Filed March 18, 1955 j )fl 7a I? y 2@ A Z A 7 Yala/'MAS muy( United States Patent O 3,123,792 SWITCH-RHEOSTAT Julius R.Klemm, Wilmette, Ill., assignor to Dowst Manufacturing Company, acorporation of Illinois Filed Mar. 18, 1963, Ser. No. 265,973 6 Claims.(Cl. 338-100) This invention relates to a switch-rheostat assembly and,particularly, to a pressure sensitive device in which initial operationthereof will close the switch, and the continued application of pressurewill vary the resistance of the device.

A switch-rheostat of the type that will respond to slight changes inpressure is particularly useful with games in which a variation inelectrical current is desirable for varying the speed of such toys aselectric trains or model racing cars. To be acceptable, such a devicemust have a long life and oe capable of hard usage since it is to behandled by youngsters. The switch-rheostat to be marketable must at thesame time be inexpensive to manufacture and suiciently sensitive so thatit will respond to slight changes in pressure. This sensitivity willminimize, if not eliminate, finger fatigue. While it is particularlyadaptable to racing games in which reasonably accurate speed control isa factor, it is not limited to such a use.

It remains to note that the device is designed so that it willautomatically be returned to the open position when the finger pressureis released to prevent the switch from remaining in the on position.

In accordance with the present invention, there is provided a housingassembly within which are disposed a pair of spaced contacts. Tocomplete the circuit, there are interposed between the contacts a switchmember and an electrically conductive material, the resistance of whichwill vary in accordance with the pressure applied there- An increase inpressure imposed on the electrically conductive material acts to lowerthe resistance and thereby increase the current flow to the articlebeing controlled thereby, and conversely a decrease in pressureincreases the resistance and decreases the current flow. In the case ofa toy racing car, the speed will be varied depending on the pressureapplied by the operator.

In the instant case, one of the contacts is resiliently biased out ofengagement with the switch member whereby when the switch is notoperated it will remain in the open position. When the spaced contact ismoved into engagement with the switch member, the circuit is closedbetween the contacts wherein current Hows from the one contact throughthe ball switch and electrically conductive material to the othercontact. The application of additional pressure compresses theelectrically conductive material to reduce the resistance thereof andcorrespondingly increase the current flow through the switch-rheostat.When the pressure is released from the device, the contact previouslyretained in engagement with the switch member is moved away therefrom toopen the switch and the pressure imposed by the switch member on theelectrically conductive material is released with a correspondingincrease in resistance. When carbon granules are used as theelectrically conductive material, a resilient compressible member isdisposed within the recess containing the granules. When the granulesare compacted, this member will compress and when the pressure on thegranules is released the compressible member expands to return thegranules to their uncompacted condition.

The structure by which the above and other advantages of the inventionare attained will be described in the following specification, taken inconjunction with the accompanying drawings illustrating a preferredstructural embodiment of the invention, in which:

FIGURE l is a perspective view of a switch-rheostat assemblyincorporating the present invention;

Patented Mar. 3, 1964 ICC FIGURE 2 is a cross-section of the deviceillustrated in the switch open position;

FIGURE 3 is a cross-sectional view similar to FIGURE 2, but showing theswitch closed and the electrically conductive material in a compactedcondition; and b FIGURE 4 is a plan View of one of the contact memers.

As illustrated in FIGURE 2, the novel switch-rheostat embodying thepresent invention is made up of a plastic housing 1 consisting ofreadily separable sections 2, 3. The housing is of a molded constructionin which the upper section 2 is formed with an inwardly extendingannular lip 4, and the lower section 3 is formed with an outwardlyextending lip 5. The inner diameter of the inwardly extending lip 4 isless than `the outer diameter of the outwardly extending lip 5 toprevent the halves from separating once the device is assembled. Thehousing is sufficiently resilient to permit enough relative movementtherebetween to assemble the two housing sections. However, once thedevice is assembled, the interengaging lip portions act to preventseparation of the housing sections during normal usage.

The housing sections 2, 3 are each provided with slits 2a, 3a,respectively, to receive contact members 7, 8. The other ends of thecontacts 7, 8 are soldered or otherwise secured to leads 10, 11,respectively. The ends of each of the contacts extending into thehousing sections are formed with a punched tongue portion 7a, 8a that isadapted to engage with the inner wall 2b, 3b of housing sections 2, 3,respectively. The tongue prevents removal of the contact from itsrespective housing once it is assembled in position (see FIGURES 2 and4).

The sections 2, 3 of the housing l are maintained in the spaced positionshown in FIGURE 2 by a sleeve 13 made of an elastomeric non-conductivematerial. The sleeve 13 is fitted into the upstanding tubular portion 14of the lower housing 3 and extends above the top thereof wherein itengages an inner wall 2c of housing section 2. The resilient sleeve 13denes a substantially spherical cavity in which is located a ball orswitch member 16. The upper portion of the sleeve extends above the balland biases the housing section 2, and contact member 7 out of engagementwith the ball 16. Thus, when the switchrheostat is in the position shownin FIGURE 2, i.e., the inoperative position, the circuit between thecontact members 7, 8 is open.

The lower portions of the sleeve 13 and ball 16 form with the lowerhousing 3 a cavity or recess 18 in which is located an electricallyconductive material, such as a plurality of carbon granules 2l). Thegranules 20 are sealed in the recess by the sleeve 13 and ball 16 whichthus gives the device a long life since the carbon granules will bepositively retained in the recess at all times. The granules may be ofany suitable size and shape, and commercially available configurationsare usable in this device. The quantity of granules located in therecess is such as to substantially iill the recess when in a loose oruncompacted condition.

When the switch-rheostat is operated, pressure is applied as shown inFIGURE 3 against the upper housing section 2. During the movement fromthe position shown in FIGURE 2 to that shown in FIGURE 3, the downwardmovement of the upper housing section moves the contact 7 intoengagement with the switch member 16 to close the circuit between theleads 10, 11. The application of additional downward pressure againstthe upper housing section urges the ball 16 downwardly to compress thelower portion of the sleeve 13 and compact the carbon granules 20located in the recess. The resistance variation in the carbon granulesis obtained by varying the contact resistance therebetween so it can beseen that the application of pressure to compact the granules throughthe application of pressure against the ball and sleeve will reduce theresistance of the carbon granules. The built-in resiliency of the sleeve13 will return the ball to the position shown in FIGURE 2 when thefinger pressure is released from the housing. The pressure against thegranules is thus released to allow them to return to their uncornpactedcondition. The interface relationship between the carbonV granules willtend to return them to the uncompacted state when the switch returns tothe off position.

To facilitate the return of the carbon granules to the uncompactedcondition, a resilient compressible ball member 21 may be located in therecess 18 containing the carbon granules. When the granules arecompacted by the compressing action exerted by the ball and sleeve, thegranules 20 distort the compressible ball 21 as shown in FIGURE 3. Thisaction sets up a reaction force tending to expand the ball when thepressure thereon is released. When the pressure applied to the upperhousing section is reduced or eliminated completely, the compactionforce acting on the granules is correspondingly changed, thus allowingthe compressible member to return to its normal conguration. During thislatter movement, the granules in the recess are loosened up, whichincreases, the resistance thereof. For example, the resistance can beset to vary between 500 and 5 ohms, Vdepending on the quantity of carbongranules and the pressure applied thereto.

Another advantage of this device is that the switch will be turned offif it is accidentally held in the normally closed position for aninordinate length of time. While the theory upon which this is based isnot completely understood, the continued application of heat to theunit, due to current iiow, results in expansion of internal parts, whichbreaks the contact between the switch member 16 and the upper contact 7.

While a particular embodiment has been described and illustrated, it isto be understood that the invention is not so limited. For example, theswitch member and rubber seal supporting the same could be of anysuitable design, and other equivalent means could be` employed forresiliently supporting the switch member in place in the device. Othermodifications could include the replacing of the compressible ball inthe recess with a springbiased plunger, or other mechanism which wouldyield in response to the pressure of the compacted granulesand wouldexpand upon release of said pressure to return the granules to theuncompacted condition. Similarly, the switch-rheostat could employ otherelectrically conductive materials that would vary in resistanceaccording to the pressure applied thereto, such as foam plastic orrubber impregnated with carbon.

It is, of course, intended to cover by the appended claims all suchmodications and embodiments that fall within the true spirit and scopeof the invention.

I claim:

1. A switch-rheostat comprising a pair of telescopically and slidablyarranged housing sections, means on each of said sections cooperating toprevent inadvertent separation thereof, the first of said sectionsdening a recess, particulate electrically conductive material in saidrecess, a lirst contact member in said first section in electricalcontact with said material, a conductor member in said 2. Theswitch-rheostat of claim l in which said housing sections arecylindrical in configuration and said means comprises an externalannular bead on said first housing section and an internal annular beadon said second housing section.

3. The switch-rheostat of claim 1 in which said conductor membercomprises a metal ball.

4. The switch-rheostat of claim 3 in which said sleeve is open-ended anddisposed coaxially of said iirst housing section, said sleeve snuglyencasing said ball and extending beyond the extremitiesV thereof. Y

5. vThe switch-rheostat of claim l in which resilient compressible meansis positioned Within said material for decompressing said material uponrelease of said second housing section.

6. A switch-rheostat comprising a pair of opposed Vtelescopically andslidably arranged cylindrical housing sections, an annular external beadon the bottom section, an annular internal bead on the top section, saidbeads cooperating to prevent inadvertent'V separation of said sections,said bottom section dening a recess, a plurality of carbon granules insaid recess, arst contact member in said bottom section adjacent thebottom edge thereof and in electrical Contact with said carbon granules,an open-ended tubular elastomeric sleeve positioned in said bottomsection above said carbon granules, a metal ball encased in said sleeveso that the top andl bottom edges of said sleeve extend beyond saidball, said ball and the bottom portions of said sleeve cooperating tovafford a seal for retaining said granules in said recess, a secondcontact member in said top section adjacent the top edge thereof, thetop edges of said sleeve normally retaining said second contact memberin spaced relation with said metal ball, said top section beingdownwardly movable whereby said second contact member rst contacts saidmetal ball to close the circuit between said contact members and furthermovement thereof causes said metal ball to compress said carbon granulesto vary the resistance thereof, and a compressible ball positioned insaid carbon granules for decompressing said granules upon release ofsaid top section.

References Cited in the le of this patent UNITED STATES PATENTS 740,787Vetter Oct. 6, 1903 1,159,674 Honold Nov. 9, 1915 2,333,814 Perkins Nov.9, 1943 2,367,441 Schwinn Jan. 16, 1945 2,394,271 Taylor Feb. 5, 19462,475,696 Cornish July 12, 1949 2,856,492 Heyhal Oct. 14, 1958

1. A SWITCH-RHEOSTAT COMPRISING A PAIR OF TELESCOPICALLY AND SLIDABLYARRANGED HOUSING SECTIONS, MEANS ON EACH OF SAID SECTIONS COOPERATING TOPREVENT INADVERTENT SEPARATION THEREOF, THE FIRST OF SAID SECTIONSDEFINING A RECESS, A FIRST CONTACT MEMBER IN SAID FIRST SECTION INELECTRICAL CONTACT WITH SAID MATERIAL, A CONDUCTOR MEMBER IN SAID FIRSTSECTION ADJACENT SAID MATERIAL, A SECOND CONTACT MEMBER IN THE SECONDHOUSING SECTION, AND A RESILIENT SLEEVE IN SAID FIRST HOUSING SECTIONAND SUPPORTING SAID CONDUCTOR MEMBER RELATIVE TO SAID MATERIAL AND SAIDSECOND CONTACT MEMBER IN SPACED RELATIONSHIP WITH SAID CONDUCTOR MEMBER,SAID SECOND HOUSING SECTION BEING SLIDABLE AXIALLY WHEREBY SAID SECONDCONTACT MEMBER FIRST WILL ENGAGE SAID CONDUCTOR MEMBER TO CLOSE THECIRCUIT BETWEEN THE CONTACT MEMBERS AND FURTHER MOVEMENT THEREOF WILLCOMPRESS SAID MATERIAL TO DECREASE THE RESISTANCE THEREOF.